1. Field of the Invention
This invention generally relates optical filters to provide eye protection from an intense light source and more specifically to a replaceable, quick connect cartridge for use in welding helmets.
2. Description of Related Art
Welding helmets have been used for a significant period of time to protect a welder""s eyes during the welding process. Protection is afforded by placing a relatively opaque filter between the welder""s eyes and an arc that is an intense light source. Early filter designs, still in use, rely upon fixed optical density filters or passive filters. These passive filters have the advantage of presenting a large viewing area. However, a welder can not see a work piece with such a filter in place unless an arc is present or the work piece is brightly lit. Although proper welding procedures and techniques involve placing the welding tool proximate the work piece, lowering the face plate then striking the arc, in practice an alternative procedure has evolved. The welder swings the face mask with the eye protection into a nonobstructing position and then seeks to drop the face mask in place exactly at the time the arc is struck be snapping the head. Consequently welders are prone to suffer eye, face and neck injuries.
More recently auto-darkening welding filters have come into use. These filters are formed of liquid crystal display (LCD) cells that can be electrically driven between a relatively transparent state and an relatively opaque state. LCD displays have been gaining acceptance because they are easier to use. Fast acting LCD devices have the advantage of allowing the welder to retain the welding helmet in place thereby to allow relatively direct viewing of a work piece prior to striking an arc while an LCD device exhibits the reduced density characteristics. A photodetector senses the onset of the arc and darkens the filter in sufficient time to avoid eye damage by rapidly shifting the LCD to its first optical density. Thus the auto-darkening welding filters have the advantage of eliminating a cause of many injuries.
However, liquid crystal displays have limited sizes and are not available to a size corresponding to the size of passive filters. As a result auto-darkening welding filters can severely restrict a welder""s field of view during the welding process.
Although many welding masks include integral, permanent viewing filters, in recent years the concept of using such a filter in a cartridge sense has enabled the use of a single welding helmet with cartridges of different shades. For example, U.S. Pat. No. 4,774,723 (1988) to Ruck discloses a welding helmet with a mechanism for supporting a lens pack in a port through the helmet. In a released position, the assembly permits the lens pack to be removed for exchange or other purposes. U.S. Pat. No. 5,062,156 (1991) to Siegal discloses another version of a cartridge in which a ledge supports a filter plate adjacent a view port.
There have also been efforts to incorporate an LCD variable density filter in such cartridges. For example, U.S. Pat. No. 5,533,206 (1996) to Petrie et al discloses an easily removable, electronic quick change cartridge that is retained in an cartridge housing. The cartridge is self-contained. That is, it includes an LCD device with battery holders and circuitry for allowing the LCD device to operate. However, viewing is limited to only that area of the LCD when an arc is struck.
Efforts also have been undertaken to produce welding masks that have different viewing areas for different conditions. For example, U.S. Pat. No. 4,155,122 (1979) to Budmiger discloses a welder""s helmet with a window having an upper section and a lower section. The upper section has an invariable light attenuation characteristic. The lower section comprises an ultraviolet filter, an infrared filter and an electro-optical shutter such as a liquid crystal, sandwiched between a polarizer and an analyzer. A control circuit including a UV sensitive photocell operates the shutter to reduce the amount of light transmitted through the lower section of the window. In this structure each of the upper and lower sections are discrete elements mounted in a frame that also carries simple circuitry for operating the liquid crystal.
In U.S. Pat. No. 5,140,707 (1992) to Johnson a helmet has an observation aperture through a face portion that supports a lens assembly. This assembly includes a first lens that overlies the observation aperture. The helmet also carries a second lens system. Each of the lens systems can be independently pivoted over the observation aperture to provide different levels of light attenuation or transmission.
U.S. Pat. No. 5,669,070 (1997) to Bennett et al. includes a face protecting shroud with an aperture and a filter. The filter has a first viewing region through which the operator may safely view the work piece during activities generating potentially damaging radiant energy and a second, adjacent region for viewing the work piece during activities not generating potentially damaging radiant energy. It is apparently the intent of this patent to provide a helmet in which a welder looks through one area during welding and another area when the arc is off. The first viewing region comprises two stacked filters to increase light attenuation over that provided by the second viewing region that includes only a single filter.
Collectively these references present as prior art welding helmets with removable cartridges using either passive filters or LCD variable density filters. However, prior art welding helmets with LCD devices have only limited viewing through a portion of a total viewing area for a comparable sized passive filter. Thus while passive filters can provide a large viewing area, they do not incorporate the dual density and attenuation advantages of an LCD device. What is needed is a self-contained replaceable cartridge that provides extended viewing during a welding operation and incorporates the advantages of an LCD device.
Therefore it is an object of this invention to provide an improved electronic quick change cartridge that is readily adapted for use in a conventional welding helmet.
Another object of this invention is to provide an electronic quick change cartridge that has an expanded viewing area in the presence of intense light as from an arc.
Still another object of this invention is to provide an electronic quick change cartridge for a welding helmet that provides an expanded viewing area when an arc exists during a welding operation.
Yet another object of this invention is to provide a quick change cartridge for a welding helmet that provides expanded viewing during welding and incorporates the advantages of an LCD device.
In accordance with this invention, an optical filter assembly for protecting eyes in an environment having a switchable intense light source includes a base, a filter, a control circuit and an opaque filler. The base has an aperture therethrough, a cavity spaced from the aperture and a channel interconnecting the aperture and the cavity, and the base is formed of a material having a fixed light transmission characteristic. The filter, disposed in the aperture, switches between a first optical density corresponding to the fixed light transmission characteristic of the base and a second, reduced optical density. The control circuit, that mounts in the cavity and connects to the filter through the channel, controls the optical density of the filter in response to the presence of the intense light. The opaque filler is in the cavity and the channel. An individual has substantially uniform vision through the filter and the base in the presence of the intense light and through the filter in the absence of the intense light.
In accordance with another aspect of this invention, a replaceable optical cartridge for insertion in a welding helmet protects a welder""s eyes from the intense light of a welding arc while enabling the welder visibility therethrough in the absence of the arc. The cartridge includes a base, a liquid crystal display filter, a control circuit and an opaque filler. The base has an aperture therethrough, a cavity spaced from the aperture and a channel interconnecting the cavity and the channel, and the base, has a predetermined shade number. The liquid crystal display filter mounts in the aperture and responds to a control signal by switching operating between a first light transmission characteristic corresponding to the predetermined shade number and a second, greater light transmission characteristic. The control circuit mounts in the cavity and connects to the filter through the channel for controlling the operation of the filter in response to the presence of an arc. The opaque filler is in the cavity and the channel. With this structure a welder has substantially uniform vision through the filter and the base in the presence of the arc and vision through the filter in the absence of the arc.
In accordance with yet another aspect of this invention, an integral sealed exchangable optical filter for protecting a welder""s eyes from the radiation produced by a welding arc includes a base, a variable filter, a control circuit and a filler. The base, composed of a polycarbonate having a given optical density, provides a predetermined light attenuation. The base includes an aperture therethrough, a cavity spaced from the aperture and having at least one passage therethrough and first and second channels between the aperture and the cavity. The variable filter disposed in the aperture provides first and second light attenuations in response to a control signal. The first light attenuation corresponds to the predetermined light attenuation and is greater than the second light attenuation. The control circuit mounts in the cavity and includes a monitor in one passage for switching the variable filter between the first and second attenuations in response to the presence and absence of an arc. The control circuit connects to the variable filter through the channels. The filler lies in the cavity and the channels to augment light attenuation. The structure provides a welder with visibility through the filter in the absence of an arc and through the filter and portions of the base in the presence of the arc.